1. Field of the Invention
The present invention generally relates to a signal processing system, and, more particularly, to a signal processing system, in which a receiving adapter unit is interposed between a keyboard and a signal processing unit, and in which switch data obtained by the keyboard is transmitted to the receiving adapter unit through a cable or as a light signal.
2. Description of the Related Art
Generally, in the case of connecting a keyboard to a signal processing unit such as a personal computer (PC), the signal processing unit and the keyboard are connected with a cable. When one of many keys provided on the keyboard is operated, a switch code (namely, a keyboard code) corresponding to the operated key is formed in the keyboard. This switch code is transmitted to the signal processing unit through the cable.
Referring now to FIG. 5, there is shown a block diagram illustrating the configuration of an example of a known signal processing system in which a keyboard is connected to a signal processing unit through a cable.
As illustrated in FIG. 5, the signal processing system is configured by connecting a keyboard 51 to a signa processing unit (PC) 53 through a cable 52. In this case, the keyboard 51 consists of: a key matrix 54 in which many keys are placed; a control portion (namely, a control processing unit (CPU)) 55 for supervising and controlling an operation of the entire keyboard by controlling (or managing)control data supplied from the signal processing unit 53; an indicating portion (IND) 56 for displaying operating conditions of the keys and so forth; and an interface circuit (I/F) 57 for interfacing between the keyboard 51 and the signal processing unit 53. In this case, the control portion 55 carries out the following various functions. Namely, a first one of the functions is to generate a scanning signal for sequentially scanning many keys provided on the key matrix 54. Further, a second one of the functions is to receive switch data corresponding to operated one of many keys that are scanned. Moreover, a third one of the functions is to convert accepted switch data into a switch code to be sent to the signal processing unit 53. Furthermore, a fourth one of the functions is to transmit the switch code to the signal processing unit 53 through the interface circuit 57 and the cable 52. Additionally, a fifth one of the functions is to transmit predetermined indication data to the indicating portion 56. Besides, a sixth one of the functions is to perform predetermined signal processing in response to a command signal supplied to the control portion 55 from the signal processing unit 53 through the cable 52.
When some (namely, one or more) of the many keys placed on the key matrix 54 are operated in the signal processing system having the aforementioned configuration, the control portion 55 receives switch data, which respectively correspond to the operated keys, in sequence. Subsequently, the control portion 55 converts the received switch data into switch codes to be sent to the signal processing unit 53. Then, the control portion 55 transmits the switch codes to the signal processing unit 53 sequentially through the interface circuit 57 and the cable 52. If some command data is supplied to the control portion 55 from the signal processing unit 53 during transmitting these switch codes, the control portion 55 performs an operation, which corresponds to the contents of a command represented by the command data, in response to the command data.
Further, among known signal processing systems, there has been developed what is called a wireless keyboard, which is wirelessly connected with a signal processing unit by transmitting light signals such as an infrared light signal therefrom so that the light signal is received by the signal processing unit, instead of connecting a signal processing unit therewith through a cable. An example of such a system is disclosed in the Japanese Unexamined Patent Publication No. 2-304611.
Meanwhile, the known signal processing system, in which a keyboard and a signal processing unit are connected with each other through a cable, has problems in that kinds or types of keyboards, which can be connected to the signal processing unit, are limited, that in addition, kinds of data, which can be transmitted between the keyboard and the signal processing unit, is limited to switch data and so on, which can be processed in the signal processing unit and that thus, the data transmission performed in the signal processing system lacks flexibility.
On the other hand, the known signal processing system, in which a keyboard and a signal processing unit are wirelessly connected with each other by transmitting a light signal, has similar problems in that the kind of a keyboard, which can transmit data to and received data from the signal processing unit, is limited to a wireless keyboard, that in addition, kinds of data, which can be optically transmitted between the keyboard and the signal processing unit, is limited to switch data and so forth, which can be processed in the signal processing unit and that thus, the data transmission performed in the signal processing system lacks flexibility.
The present invention is accomplished to solve these problems of the known signal processing systems.